Event-specific versus unitary causal accounts of optimism bias.

Optimism bias is often assumed to have a unitary cause regardless of the event, however, factors causing it may actually be event-specific. In Experiment 1 (N = 23), subjects rated the importance of various causes for individual events. The results identified consistent differences in perceptions of causal factors across events. Experiment 2 (N = 190) employed the possible causal factors absent/exempt error and degree of motivation to investigate an event-specific theory of optimism bias in a manipulation design. Participants were encouraged to view one causal factor (absent/exempt or motivation) as either important or unimportant to future risk when they estimated their risk of absent/exempt-related, motivation-related and unrelated events (as determined in Experiment 1). A hanging control group received no manipulation. The event-specific theory's prediction that these manipulations would affect particular events and not others were not supported. However, discouraging the absent/exempt error reduced optimism bias across events, generally. Hence, a unitary and not an event-specific theory of optimism bias was supported. Furthermore, for the first time, the possible role of and confounding of cognitive manipulations of optimism bias by mood were evaluated, and not supported.